Revert "[FIR] Implement INVISIBLE_SETTER"

This reverts commit b3d7ed56

compiler/testData/diagnostics/tests/controlFlowAnalysis/kt2960.fir.kt

@@ -0,0 +1,36 @@
+//KT-2960 Perform control flow checks for package property initializers
+
+package b
+
+class P {
+    var x : Int = 0
+        private set
+}
+
+val p = P()
+var f = { -> p.x = 32 }
+
+val o = object {
+    fun run() {
+        p.x = 4
+
+        val z : Int
+        doSmth(<!UNINITIALIZED_VARIABLE!>z<!>)
+    }
+}
+
+val g = { ->
+    val x: Int
+    doSmth(<!UNINITIALIZED_VARIABLE!>x<!>)
+}
+
+class A {
+    val a : Int = 1
+      get() {
+          val x : Int
+          doSmth(<!UNINITIALIZED_VARIABLE!>x<!>)
+          return field
+      }
+}
+
+fun doSmth(i: Int) = i